1. Field of the Invention
The present invention relates to a method and an apparatus for monitoring abnormality of a mold-clamping mechanism of a molding machine, and particularly relates to a method and an apparatus for monitoring abnormality of a mold-clamping mechanism of a molding machine, capable of measuring the amount of aged deterioration of a mold-clamping mechanism used in a die casting machine, a resin injection molding machine or the like and judging the timing of inspection and maintenance of the mold-clamping mechanism.
2. Description of the Related Art
In molding machines typified by die casting machines and resin injection molding machines, many of them with use of toggle mechanisms for mold-clamping mechanisms are used for the purpose of obtaining large mold clamping force.
Such molding machines are operated for long years (5 to 10 years), and as a result, abrasion occurs to the rotational shaft bearing portions for connecting the links and the pins constituting the toggle mechanisms. When the abrasion increases, deviation occurs to the mold clamping force, whereby the problem that burrs generate at the mating surfaces of the metal mold or the toggle mechanism passes the change point (dead point) and the molds cannot be opened after the injection molding. Consequently, for the purpose of preventing these troubles, the mold-clamping mechanisms are disassembled periodically and direct measurement is performed to find out whether the abrasion amounts at the pins and shaft bearing portions exceed a threshold value.
However, the aforementioned conventional method requires tremendous workers"" effort for disassembly inspection and re-assembly of the mold-clamping mechanism. Further, the expense for inspection and stop of the molding machine become necessary, which reduces productivity of the entire factory and causes great loss.
A method of attaching sensors to tie-bars constituting a mold-clamping mechanism and judging the deviation of the mold-clamping force with reference to the values from the sensors is known, but direct measurement of the toggle mechanism is not performed, and thus it is difficult to judge the degree of each abrasion at rotational bearing portions for connecting links and pins (constituting the toggle mechanism).
Disassembly inspection is effective only for secular change in abrasion, and an unexpected abnormality occurring during the operation of the molding machine (for example, increase in rotation load caused by poor lubrication at the rotating portions) cannot be monitored.
In view of the aforementioned conventional problems, an object of the present invention is to provide a method and an apparatus for monitoring abnormality of a mold-clamping mechanism of a molding machine, which estimate abrasion amount without disassembly inspection of the mold-clamping mechanism in the molding machine, make it possible to operate the machine until the time just before a quality deficiency of the product occurs, perform maintenance with the minimum disassembly inspection and improve productivity, and can detect an abnormal phenomenon even if an unexpected abnormality occurs to the mold-clamping mechanism.
A method and an apparatus for monitoring abnormality of a mold-clamping mechanism of a molding machine, which estimate an abrasion amount without disassembly for inspection of a mold-clamping mechanism in a molding machine and make it possible to operate the machine until the time just before a quality deficiency of a product occurs, perform maintenance with the minimum disassembly for inspection and improve productivity, are provided.
A die casting machine 10 uses a toggle mechanism 30 for a mold-clamping mechanism 16, and a strain gauge 40 is stuck to the toggle mechanism 30. The strain gauge 40 is connected to stress judging means 47 via a signal amplifier 42. The abrasion amount is calculated from the recorded data and the timing of maintenance of the mold-clamping mechanism is judged from the correlation between the abrasion amount and the quality of a molded product in the stress judging means 47, thereby making it possible to perform maintenance with the minimum disassembly inspection and improve productivity.